The invention relates to a combined supporting roller-friction drive arrangement for overhead single-panel doors, particularly for garages or the like. Such arrangements comprise in the upper edge zone of the door panel on both sides respectively one projecting drive roller coupled to a drive mechanism--especially of the electric motor type--for rotation therewith. These projecting drive rollers engage fixed guide tracks extending approximately horizontally with the drive rollers being held, with respect to their mounting at the door panel to be adjustable in such a way that, in the closed position of the door panel, the respective drive roller is under pressure by a spring load approximately vertically toward the bottom of the guide track, to ensure a friction engagement between the drive roller and the bottom of the track.
Single-panel doors are fastened by means of an articulated linkage. Consequently, the guide rollers laterally projecting in the upper edge zone of the door panel do not execute a linear motion in the tracks, which tracks extend approximately horizontally. Particularly in the initial phase of the movement from the closed position into the opened position, the supporting drive rollers describe an upwardly curved path, and on account of this fact the drive rollers, in case of linear guide tracks, are not constantly in engagement with the bottom of the guide tracks. Attempts have been made to take these motion processes into consideration by arranging the running tracks at the ends on the frame side to be displaceable under spring force so that the guide tracks follow the drive rollers, to achieve the result that the drive rollers remain in contact with the bottom of the guide track in any phase of motion. Such a construction is relatively expensive and relatively cumbersome especially in view of the mass of the guide tracks controlled by spring force.
It has also been contemplated to construct the mounting of the supporting and friction drive rollers so that they can be exposed to a spring load in the direction toward the bottom of the guide track. Although this system affords advantages with regard to the masses to be moved under spring force, the spring load is dependent on the angle with respect to the bottom portion of the guide tracks during the course of the movement, i.e. in the closed position the springs urge the drive rollers approximately vertically onto the guide bottom, whereas in the opened position of the door the pressure component extends practically in the direction of the guide tracks so that there is hardly any pressure component exerted on the drive rollers which is directed toward the bottom of the guide. Considering the drive relationships dynamically, a satisfactory result can be obtained in such a spring-loaded pressure roller system if the door is moved without interruptions from the closed position into the opened position and vice versa, but if there are obstacles of any kind, for example by an intermittent wind pressure or the like, it can happen that the drive rollers no longer find sufficient frictional hold on the bottom of the guide tracks to continue the movement of the door in the intended direction. Thus, the door is arrested in a certain intermediate position and/or undesirably the smooth motion process is interrupted.
The invention contemplates an arrangement which ensures that a door of the type under consideration herein, with the arrangement described in the foregoing, can be moved under any circumstances smoothly and without disturbances from the closed position into the opened position and vice versa.
This object is attained in accordance with the invention by providing that a bearing bracket is rotatably mounted to the drive roller axle, with two counterpressure rollers arranged to be displaced in the direction of movement of the drive rollers and engaging underneath the running track being supported at this bearing bracket.
It is basically conventional to ensure the frictional drive of motor-driven rollers on guide tracks by the provision of a counterpressure roller (for example U.S. Pat. No. 3,202,415). However, these prior disclosures are limited to the feature of providing, in principle, a sufficient contact pressure, independently of the weight of the door to be moved. So-called sectional doors are involved which have a drive element mounted in front thereof which insofar operates independently of the weight of the door and is not concerned with the aforedescribed problems encountered in connection with an arcuate movement of the rollers of a single-panel door.
In accordance with the invention, the drive rollers driven by the drive mechanism and mounted adjustably under spring load at the door panel are held in any imaginable motion situation in secure frictional contact with the bottoms of the guide tracks. In this connection, it is to be kept in mind that, due to the motion, a pivoting of the bearing bracket takes place which ensures that, in dependence on the closing or opening motion, respectively one of the counterpressure rollers contacts the bottom of the running track.
In a preferred embodiment, the axles of the counterpressure rollers are held at the bearing bracket in the direction toward contacting the lower outside of the running track under spring load. This feature supports the intended pressure contact of the roller against the bottom of the running track.
In another preferred embodiment, the axles of the counterpressure rollers are vertically adjustable in the direction toward the axle of the friction roller.
Finally, in a further preferred embodiment of the invention, the bearing bracket is fashioned in its upper zone so that it extends over the running track; consequently, the door is secured from falling off in case the rollers can no longer execute their supporting function. Such a safety feature is known per se in isolation, but not in the novel combination of the present invention.
These and other objects, features and advantages of the present invention will become more apparent from the following description when taken in connection with the accompanying drawings, which show, for purposes of illustration only, a single embodiment in accordance with the present invention.